U-tube manometer



May 27, 1958 H. A. QUIST 2,836,067

-U-TUBE MANOMETER Original Filed Dec. 24, 1952 3 Sheets-Sheet 1 Open To Atmosphere iii-32 L 1E, "a L) IN V EN TOR. HAROLD A. QUIST ATT RN May 27, 1958 H. A. QUIST 2,836,067

U-TUBE MANOMETER Original Filed Dec. 24, 1952' 3 Sheets-Sheet 2 IN VEN TOR. HAROLD A.QUIST AT ORNEY May 27, 1958 H. A. QUIST 2,836,067

U-TUBE MANOMETER Original Filed Dec. 24, 1952 3 Sheets-Sheet 3 IN VEN TOR. HAROLD A. QUIST "Dc/eh. lw

ATTORNEY Unite States Patent C) assaosr U anus MANQMETER Harold A. Quist, Swarthmore, Pa., assignor to Sun Oil Company, Philadelphia, Pa, a corporation of New Jersey Original application December 24, 1952, Serial No. 327,726, new Patent No. 2,760,373, dated August 28, 1956. Divided and this application September 21, 1955, Serial No. 535,571

3 Claims. (Cl. 73-491) This invention relates generally to liquid level measuring devices and particularly to such devices which translate liquid pressures by liquid means into an indication of the elevation of the liquid level.

Devices of this type have not been sufiiciently accurate, in the past, because of natural and structural difficulties experienced on both the liquid-level sensing end and the indicating or recording end or the systems. Taken together the errors encountered in the respective parts of such a measuring device were cumulative and resulted in erroneous readings.

Considering the liquid-level sensing elements separately from the indicating mechanism, the prior art frequently uses the pressure existing in the body of the stored liquid as the operating means. This is accomplished by placing a pressure responsive means adjacent the bottom of a storage tank or other receptacle and reading the results on a liquid column connected thereto. Such a device does not consider the effects of temperature changes nor the Stratified variations in specific gravity present in the liquid mass to be measured, as existing, for example, in petroleum products. It is an object of this invention to provide a device which receives and accurately indicates all changes in liquid level as a function of pressure, free of the characteristics of the stored liquid as sensed by separate apparatus such as is disclosed and claimed in application Serial Number 327,726, filed December 24, 1952, now Patent No. 2,760,373, issued August 28, 1956, of which this case is a division.

Having accurately positioned the level of a body of liquid by the level sensing end of the mechanism, it is necessary to transmit that information to an equally accurate device for indicating or measuring it. The transmission of this pressure to an indicator such as a manometer reading liquid level in terms of liquid pressure has, in the past, been subject to several disadvantages. A direct reading for large storage tanks, as in the petroleum industry, has required measuring tubes of equal height. If the elements of such an indicator were reduced, accuracy was lost and the device worthless. it is, therefore, a further object of this invention to provide a liquid level indicator, liquid operated, adapted to amplify the changes in liquid levels for accurate fractional reading, yet is of a size easy to install and read.

In the petroleum industry, it is necessary to consider volatile liquids which form a large part of the stored products. The marketable value of such volatile products is based upon their respective volumes at an agreed temperature. As this agreed temperature is seldom, if ever, that of either a part or the average of the stored volume, it is necessary to know the temperature, particularly the average temperature of the stored liquid, to adjust the liquid volume accordingly. It is, therefore, still another object of this invention to facilitate the determination of volumes of stored volatile liquids with a high degree of accuracy.

' ecarne With these and further objects in view, the invention consists in the arrangement and combination of the parts hereinafter described, claimed and shown in preferred form in'the drawing in which:

Figure 1 is an elevational view partly in section, graphically representing the device as applied to a fixed roof storage tank.

Figure 2 is a section of Figure 1 taken along line 2-2.

Figure 2A is another sectional view of Figure 1 taken along line 2A-2A.

Figure 3 is an elevational view partly in section, graphically representing the device as applied to a floating roof storage tank.

Figure 4 is an elevational view, in perspective, of a preferred form of the level indicator.

The remote indication of liquid levels by means of pressure through liquid means introduces problems of relative volumes as afiected by temperature. As previously indicated, in a sirnple form of device the stored liquid can be connected directly to a tall tube vertically positioned at the reading point. To be effective such an arrangement must be level with the storage tank and the liquid volume to be measured must be small. With these restrictions met, although the liquid level can be read, it is not accurate for the problem of temperature and its efiects must still be corrected.

Such a simple device as outlined above will not fill the need under present storage requirements Where very large tanks are placed at varying elevations relative to the pump or other control building. It is, therefore, necessary to confine the use of the above suggested mechanism for direct reading to storage facilities of limited size properly positioned.

As has been indicated above, to apply the principles of liquid level measurement by liquid pressure it is necessary to sense the liquid level changes by means other than the stored liquid. The efiects of natural conditions such as pressure and temperature on this level sensing means must be reasonably constant and, consequently, predictable. And finally the indicating device adapted to receive the information from the level sensing means must be within easy reach and accurate Within required limits.

According to-the present invention advantage is taken of the difference between the specific gravities of known liquids so arranged as to amplify the pressure of a column of one liquid. The initiating liquid is responsively positioned in the body or" stored liquid, to clearly indicate the stored liquid level. Additionally the controlled position of the body of pressuring liquid within the storage tank is used to determine the locus of the average temperature surrounding it, the measurement of which is necessary for accurate determination of both the liquid level nd the actual volume in the storage container. The onset of temperature differences between the level sensing end the device and the indicator is controlled by liquid selection and/or measurement, and the indicating device is maintained under constant temperature conditions. Finally, advantage is taken of the immiscibility of certain liquids to separate reading liquid columns from liquid pressure transmitting columns in a manometer of multiple legs for the additive reading of large volumes of liquid in an instrument of limited dimensions.

In the drawings, the two common forms of storage tanks requiring liquid level indicators are shown as fixed and floating roof types. A pressuring column of liquid is maintained in sensing relation with the stored liquid level by float elements which also support the temperature sensitive elements in proximity therewith. The extended manometer which adds the stored liquid depths,

' temperature-changes.

partially indicated 011 the separate legs, .s shown both graphically and as a finished instrument inthe figures of the drawing. The floating roof tank is further supplied with an additional indicating device which will be fully explained in the detailed explanation following.

7 high specificgravity such as mercury, contained in tube 18, and the additional weight of the atmosphere conducting'tube 20, the electrical conductors 22 of the temperature detecting device and the support 24 shown hinged to the bottom of the tank at 26, a double float 28' and 30 is arranged as the support. Figure 2 shows the floats 28 and 30 linked in tandem by a yoke 32 and a 'flexible wire connector 34 which permits flexibility necessitated for movement between extreme positions.

Whereas the float 30 is a simple hollow container serving no other purpose thanto buoyantly support the .2,836,067 K s a listed elements with the help of float 28, this latter float serves other purposes. Within the body of the float 28,

V a cup 36 is mounted to receive the tube 18 into the bottom thereof. The liquid 16 which fills the tube 18 is free to enter the cup and leave it as the float 28 lifts and falls.

By adjusting the quantity of heavy liquid 16 in the float 28 and tube 18, the level of the stored liquid 12 can be substantially approximated for all changes in elevation within the normal operating limits. Also tube 20, connected to the atmosphere outside the tank 10 through the drier container 21, equalizes the pressure on the liquid level sensing end of the liquid indicating device with a like atmospheric pressure at the end of the indicator, as

will be fully understood after reading the description of the operation of the device.

The temperature sensing elements are shown here as the storage tank The containers 66 and 70 are closed tubes 64 and 68 are flexible in nature and are adapted to engage and flex with the jointed mounting member 72 linking the liquid supported float 54 with the lower part of the storage tankSl) at any desired level dependent on storage conditions. 'A bracket 73 connects the hinged support 72 to the float and is supported at the proper elevation above the bottom of the tank by bracket. 75.

An electrical device for measuring the average tem perature of-the tank contents along the exterior surface of the tubes 64 and .68 includes a conductor similar to that shown in Figure l, omitted here for clarity. An electrical circuit also similar to that shown in connection with Figure 1, including a battery 76, a switch 78 and a calibrated electrical responsive iudicator80, together with the proper connecting wires, is electrically coupled'to the conductor.

To insure the balance of pressures on the sensing end of the liquid level measuring device the receptacles 56 and 58 are open to the pressure conditions above the floating roof 54. This insures atmospheric pressure eifective on the level sensing end of the mechanism which counterbalances like pressure on the open end of the indicating device to be considered later. 7 V

Reference to both Figures l and 3 will show'a graphic representation of the modified manometer used to translate a pressure of the liquid in the conduits which, by means of the float arrangements, transmits a" pressure indicative of the stored liquid level. One form the indicating device may take is shown in Figure 4. The

, simplest form is of the graphically represented device as a simple electrical conductor 22 mounted to be adjacent V the pressuring liquid. column 16 throughout its eflective length in the liquid. Electrical energy from a power source, such as the battery 40, is passed throughthe conductor 22'by operation of the switch 42. The conductor 22 is selected for its variable conductivity in response to An indicator 44, calibrated'to read temperatures as a function of this change in conductivity of conductor 22, is connected in series therewith.

The modified form of manometer shown in graphic representation to the right of Figure -1 is used as the liquid level indicating mechanism for both the fixedroof tank shown in this figure, as well as for the movable roof tank shown in Figure 3.

of this modified form of manometer will be given as relating to both types of storage tanks after the liquid level sensing device for the movable roof tank, as shown in Figure 3, has been described.

Reference to Figure 3 shows a floating roof tank in which the stored liquid 52 supports a representative i 'tainer 70 mounted on the bottom of the storage tank 50. V A like tube 68 connects the receptacle 58 with a similarly constructed container 66, also mounted on the bottom of Therefore, a description shown in Figure 1 and will be described first.

Connected to the lower end'of the tube 18, described as attached to the hingedsupport 24 and opening into the float 28, is a sealed container in which a quantity of mercury 102, or liquid of relative high specific gravity,

fills the lower portion thereof. Above the mercury in the container 100 a liquid 140, which may be water treated against freezing or a like liquid of less specific grafity than the mercury or mercury substitute, fills the mitting tube 106 may, if necessary, be buried in the ground or otherwise insulated.f k V 7 Tube 106 filled with the selected lower gravity liquid is connected to receptacle 108, which forms the initial pressure reading liquid supply receptacle of the modified manometer indicating device. In the bottom of the supply receptacle 108 a quantity of a high specific gravity liquid 110 is sufficient in volume to cover the bottom of the first reading leg 112 under all pressure conditions. This liquid 110 may either be the same as 102 previously noted, or may be different liquid. The only requirements are that the lower of .two liquids throughout this mechanism must be heavier than the liquid above it, and they must be immiscible one with. the other. The reading leg 112 is filled with a less specific gravity liquid like or similar to that used in the previously, recited elements of the device, which, because of the difference in specific gravity between the heavy and light liquids, fills the read- 7 reading liquid supply receptacle 118, which also has'a I assess? quantity of heavy liquid therein, as indicated. From the bottom of the second reading liquid supply receptacle 118, a tube 120 connects with a third form of receptacle number 122, which can be considered as a rectifier receptacle as it absorbs the differential volume created in multiplying the reading and pressure transmitting legs. The rectifier receptacle 122 is the t of a number of like volumes which are repeated throughout the indicator in varying sizes to accommodate the displaced liquid reading and pressure transfer volumes.

The second reading leg 12% rises from the rectifier receptacle 122 into the second overflow receptacle 126. From this second overflow receptacle a pressure transmitting leg 12% similar to number 116, previously described, transmits the accumulated pressure and displaced liquid volumes downwardly into the third reading liquid supply receptacle 33%, as shown. Again the accumulated volume of the preceding pressure transmitting legs is absorbed in a second rectifier receptacle numbered 134, transmitted thereto through tube connector 132.

It will be noted that the accurnulated volumes which must be received and maintained in proper level with the intermittent heavy liquid reading legs, and the lighter liquid filled pressure transmission legs, must be consecutively absorbed by the rectifier volume receptacles number 122 and 134. This is indicated, as required, in Figures 1, 3 and 4 by changing diameters of these rectifier receptacles.

It will be evident, and is indicated in connection with this Figure 1, that the number of legs may be multiplied to meet the requirements of any height which the liquid level may assume above the indica 'ng mechanism. As will be more clearly understood later in this specification, the example which explains the presently operating mechanism requires the rectifier volume of the final reading leg to be eight times that of the initial rectifier. Consequently, the drawing shows the leg structure broken and the final rectifier 335 is eight times the volume of the initial rectifier 122. it should be noted that back pressure in the device caused by the rectifier receptacles has been reduced as far as possible by maintaining the static hydraulic head at a minimum by varying the diameter, rather than the height, of the receptacles to obtain volume variations.

The basic structure 01. the indicating device shown graphically in connection with Figure 3 will be recognized as containing the same elements above described in connection with Figure l. The heavy liquid content of the sealed container 7%) is connected by water or lighter liquid through the tube 82 to the top of the initial reading liquid receptacle 8%, which has a volume of heavy liquid therein noted as 26. At this point there is a modification of the device over that previously discussed in that there is a tube connected from the bottom of liquid receptacle 34 through a single manometer element generally noted as $9 and returned through tube 92 to the top of the sealed container mounted in the bottom of the tank By means of adjusting the liquid levels to desired elevations in the float containers 56 and 58, respectively, it is possible to read a differential elevation in the indicating liquid shown as 94 having two levels both of which are shown in the manometer 99 against the scale 95 placed between them.

Returning to the stored liquid level indicating device, the initial reading leg 96 connects the overflow receptacle 98 with the initial reading liquid supply receptacle 84, as has been explained for a similar arrangement with reference to the indicator mechanism of Figure l. The remaining supply, overflow and rectifier receptacles are clearly shown and serve the same purposes in the same way as has previously been disclosed in connection with Figure l and will not be repeated here.

It will be noted that the last reading legs numbered 138 and 99 in Figures 1 and 3, respectively, are open to atmospheric pressure, which as the atmospheric pressure has been admitted to the liquid level sensing floats eliminates any necessity for introducing other means to balance this pressure, as it is effective on both open ends of the pressuring liquids. This pressure at each end of the device requires only that it be equal and balanced. A like result may be obtained by connecting to other balanced pressures or simply connecting both these open ends of the mechanism together.

To those versed in the art, the description or the elements previously given will undoubtedly indicate the operfeatures in full detail. However, to emphasize the advantages of the disclosed device and further distinguish the combination as modified from the existing art, a detailed description of the operation of the mechanism and the advantages will be given. Reference will be made to all the figures in the drawing and Figure 4 will be stressed as an economic form of indicating device developed to support the modified manometer shown graph ically in Figures 1 and 3.

Considering Figure 1 first, as a complete understanding of this figure will leave little to be added in describing Figures 3 and 4, the addition and removal of stored liquid or temperature change, for example in a stored quantity of a petroleum product, will raise and/ or lower the liquid level 14. The amount of resulting increase or decrease in stored liquid volume will be reflected by the level of the liquid standing in the storage tank by any time. This is, however, affected by temperature conditions existing in and around the tank which must be considered in obtaining the corrected liquid level from that indicated as well as correctly measuring the volume.

The float arrangement shown in Figures 1 adapted to follow the increasing or decreasi. E: liquid level 14 as it assum s its position in the storage tank regardless of whether that position has been increased or decreased over what it should be theoretically, b.- cause of temperature or other modifying conditions. By adjusting the elevation of the cup 36 relative to the fioat 23, the heavy liquid filling the tube It} can be arranged at substantially the level of the stored liquid l t for all elevations. The heavy liquid which fills the tube is thus maintained at a volume sufficiently great to reach through the tube 13 from the liquid level down to the sealed container 1% by the overflow capacity of the float 28. It will be obvious that the pivoted fioat arrangement lowered to an almost horizontal position will displace heavy liquid which will again be absorbed into the tube system as the floats lift and the tube 18 approaches a vertical position. Further as the level of the pressuring liquid 16 coincides with the level of the stored liquid, the pressure of the liquid column reflects, substantially, the physical elevation thereof.

The liquid 16, as it lifts and lowers, transmits this pressure dependent upon the vertical distance reached by the liquid level into the sealed container 3.9% wh' raises or lowers the level of the heavy liquid volume lea therein. This pressure condition is transmitted through the liquid pressure transmission medium noted above a... water or some like lighter liquid, which is transmitted in turn through tube lllfi to the initial reading liquid supply receptacle 108 in the manometer device.

The electrical conductor 22' arranged to be exposed to the different thermal strata of the stored liquid 12 may be switched on or off as desired to obtain a reading of the average temperature within that body of liquid. With this information, the known liquid level indicated on the reading legs of the modified manometer, as later described, can be volumetrically adjusted to a basic temperature for purposes of measurement. This is readily understood by those versed in the art and requires simply the consultation with prepared tables and the application of a multiplier which varies for different temperatures and different volumes.

To continue with the transmission of pressure as determined by the mercury column within the storage tank,

' tank. For example, in an experimental device a 40 foot possible liquid depth is measured by the disclosed modified manometer, using mercury and water, having 9 indicating. legs. Therefore each leg roughly measures feet elevation in the 40 foot liquid depth. This shows 'as a measurement on the initial reading leg only if the stored liquid level is within orbelow the first 5 foot mark of the storagetank reading from the bottom to the top.

Therefore, considering the stored liquid volume to be at approximately the 38 foot mark, as illustrative, the first 7 reading legs of the manometer will show complete heavy liquid or mercury columns and the eighth leg will show a column /5 filled with the heavy liquid which will stand at the 38 foot graduation.

In order to maintain the regularity of measurement in each separate reading leg of the manometer, the pressure transmitting fluid such as water or other lighter liquid must be moved upwardly through the reading leg into the overflow receptacle at the top thereof and at the same time displace a volume equal to the reading leg to transmit pressure downwardly into the successive heavy liquid containing receptacles noted above as reading liquid supply receptacles. At this point, it is necessary to introduce the rectifier receptacles which are, as indicated above, of selected volumes placed Within the manometer .circuit to absorb thepreviously accumulated volume in order to maintain the correct elevational reading of the proportionate stored liquid elevation'as the additional legs of the device are brought into use.

Reference to Figure 3 will indicate that the modifying manometers described above are used to measure'the level of the stored liquid volume in the same way and In this second experimental device, mercury is used as the pressuring liquid in the submerged tube within the storage tank and extends to fill the lower portion of? a sealed container of the pressure transmission elements. Within this pressure transmission section from the flask at the bottom of the pressure tube in the tank to. the

initial reading liquid supply receptacle, water is the pres sure transmitting medium. In the multiple legged manometer, water, treated with a coloring matter, is the pressure transmitting medium while the indicating liquid is the second of the two heavy liquids, tetrabromaethane.

This combination of mercury and tetrabromaethane separated .by water makes a very satisfactory device. As water is non-compressible and non-expansible under normal conditions, it will readily transmit the mercury column pressures to the tetrabromaethane and therebetween in the manometer. The relative specific gravities, 13.6 for mercury and 2.964 for tetrabromaethane, indicate their comparative responses. For every unit of pressure a change in the mercury, there will be approximately 4.5 times greater lineal response in the tetrabromaethane.

' Consequently, the least change in elevation of the mercury with the same results as above described.v As an additional reading particularly useful where floating roof tanks are concerned, the float 56 has measured Within it a volume of heavy liquid indicating the bottom pr contact surface of the floating roof 54. Withinthe opening 60 a volume of heavy liquid is also maintained at the level of the displaced liquid surrounding the floating roof 54. The respective pressure changes in the floats 56 and 58 are transmitted throughthe tubes 64 and .63 to the sealed containers 66 and 70. V The tubes 88 and 02 conmeet two sides of a simple manometer to receive these differential pressures. A colored liquid 94 immiscible with the pressure transfer liquid in the manometer will readily indicate, on the scale 95, the difference in elevation between the heavy liquid levelsin the respective float chambers. This gives a direct reading of the differential between elevationrof the supporting surface of the liquid and the displaced liquid surface which surrounds the float that shown in Figure 1. The shafts 300 and 332 balance the cylindrical form of the device so that it may be rotated for ease in reading. Thegraduation necessary to translate the heavy liquid height on the reading legs to an indication of the liquid level in the storage tank have been omitted from this figure for clarity. However, a

simple graduation on the tube edge or aimetallic or paper scale clipped to the tube is all that is required. To facilitate rotation, the connecting tube, here shown as 106, is flexible and permits rotation in either direction up to 180 degrees. V V The principles and structures disclosed are further applied in the form of' an additional example using two different heavy. specific gravity liquids in multiplying relation, set forth here for clarification of the invention.

is magnified many times aflording great accuracy. 1

The effect of temperature is minimized by reducing the volume of mercury used in the storage vessel to a minimum, and by adjusting the manometer reading to correct the temperature effect surrounding the modified manometer. On the level sensing end of the system, the mercury carrying conduit has an internal diameteIJapproximating inch. In comparison the volume of the chamber 36 in the float.28 is infinite. Therefore, the eflfect of temperature on the density of the mercury in the column within the conduit only need be determined. The coeflicient of expansion of mercury'at. 60, the standard for measuring volumes of petroleum Y products, is .001 andfor gasoline is .006. The net correction factor for volume calculations is, therefore, .005 at 60 degrees F.

This information can be readily calculated for: other temtrical gauge 80 or like mechanism. 7 V q The manometer, for best results, is maintained in constant temperature surroundings by using a water bath or temperature controlled atmosphere. Once established to read the pressure client in the storage vessel at 60 and maintained at a selected temperature by the control 7 adopted, only the eflect of the temperature on the mercury column in the storage vessel need be adjusted. As indi-' cated above, the volume of the stored gasoline will increase or decrease under the effects of rising or falling I temperatures. The mercury column will notbe increased or decreased in length commensurate with the rising and falling of the float, as the mercury volume in thefloated reservoir is very large compared with the small volume of the mercury column in the conduit. Therefore the height of the mercury Will always remain at the level of the stored liquid. It is necessary, only, to correct the variation in pressure caused by changes in densityof the mercury as a result of the temperature changes in the stored liquid. V V

In both applications of the device as illustrated by Figures'l and 3, means are indicated for measuring'average temperature along the pressuring column of mercury. As.

the device is calibrated at 60 F. to indicate the liquid level when both the density of the mercury in the. storage tank and the manometer liquids need no correction, this is considered as the basic reading. The change in density of the mercury for temperatures above and below the normal reading of 60 F. can be readily calculated to reflect pressure variations. Tables are prepared and applied to the manometer to adjust the reading to reflect the exact liquid level. As indicated above, once the true level of the stored contents is known, the application of presently available tables will give both the present volume and corrected volume (at 60 F.) for sales and inventory purposes.

It will be evident that a liquid level reading system is disclosed whereby liquid pressure is the operating force. By using liquid columns difierent from tl e stored liquid, the characteristics of this liquid to be measured are avoided, and the effects of natural phenomena are easily calculated and corrected. The result is a device capable of correct and exact measurement within very narrow limits.

The structure described here represents one embodiment of the device which gives these desired results. Other forms will be evident involving the spirit of the inven' tion, but avoiding the letter thereof. This invention is not to be restricted except insofar as is necessitated by the prior art and the spirit of the appended claims.

What is claimed is:

1. A manometer comprising a plurality of vertical reading legs of limited height, reading liquid supply receptacles at the bottom of each or said reading legs the initial receptacle adapted to receive pressure, separate volumes of a reading liquid in each of said supply receptacles successively visible in the reading legs, a plurality of overflow receptacles, one of said overflow receptacles disposed at the top of each of the reading legs, said reading legs extending between the bottoms of the supply and overflow receptacles respectively, pressure transmitting legs connecting the top of the overflow receptacle with the top of the next succeeding supply receptacle, pressuring liquid volumes in said pressure transmitting legs between the separate volumes of reading liquid, said pressuring liquid and reading liquid being of different specific gravities and non-miscible, and rectifier receptacles between the successive supply receptacles and the attended reading leg to absorb the accumulating VOlumCs of pressuring liquid before transmitting pressures to cause movement of the reading liquid in the affected reading leg.

2. A manometer comprising a plurality of connected legs vertically arranged and connected to successively transmit the effects of pressure and comprising alternate reading legs and pressure transmission legs, supply receptacles of equal volume at the lower juncture of each reading and pressure transmission leg, liquid of relatively high specific gravity in each of said supply receptacles in such volume as to fill its respective reading leg, overflow receptacles of equal volume at the upper juncture of each reading and pressure transmission leg, liquid of relatively low specific gravity in volumes sufiicient to fill the legs and receptacles of each reading-pressure leg pair between the respective volumes of high specific gravity liquid, the reading legs engaging the bottoms of the supply and overflow receptacles and the pressure transmission legs engaging the tops of said receptacles respectively as required by the difference of the specific gravities of the non-miscible liquids engaging each other therein, and rectifier receptacles between the respective supply receptacles and the reading legs of varying volumes to receive displaced accumulating volumes trom the legs and receptacles preceding the indicating reading leg.

3. A manometer comprising a plurality of reading liquid supply receptacles, reading legs one communicating with each of said supply receptacles and extending upwardly therefrom a predetermined height, a high specific gravity liquid in each reading liquid supply receptacle in sufiicient volume to fill the respective reading leg connected thereto, a plurality of overflow receptacles, one arranged to receive the upper end of each reading leg, said reading legs connecting the respective bottoms of the supply and overflow receptacles, pressure transmitting legs connecting the top of the overflow receptacles with the top of the next succeeding reading liquid supply receptacle forming a pressure transmitting series for liquids of different specific gravities, a non-miscible pressure transmitting liquid filling the legs between the volumes of high specific gravity liquids in the respective reading liquid supply receptacles, and rectifier receptacles of determined volume in the reading legs adjacent the reading liquid supply receptacle to receive and hold the accumulated volume of reading liquid displaced from the preceding reading and pressure transmitting legs during operation.

References Cited in the file of this patent UNITED STATES PATENTS 2,118,029 Boyd May 24, 1938 FOREIGN PATENTS 270,445 Germany Nov. 28, 1915 35,630 Denmark Feb. 4, 1926 16,372 Australia Mar. 4, 1935 

1. A MANOMETER COMPRISING A PLURALITY OF VERTICAL READING LEGS OF LIMITED HEIGHT, READING LIQUID SUPPLY RECEPTACLES AT THE BOTTOM OF EACH OF SAID READING LEGS THE INITIAL RECEPTACLE ADAPTED TO RECEIVED PRESSURE, SEPARATE VOLUMES OF A READING LIQUID IN EACH OF SAID SUPPLY RECEPTACLES SUCCESSIVELY VISIBLE IN THE READING LEGS, A PLURALITY OF OVERFLOW RECEPTACLES, ONE OF SAID OVERFLOW RECEPTACLES. DISPOSED AT THE TOP OF EACH OF THE READING LEGS, SAID READING LEGS EXTENDING BETWEEN THE BOTTOMS OF THE SUPPLY AND OVERFLOW RECEPTACLES RESPECTIVELY, PRESSURE TRANSMITTING LEGS CONNECTING THE TOP OF THE OVERFLOW RECEPTACLE WITH THE TOP OF THE NEXT SUCCEEDING SUPPLY RECEPTACLE, PRESSURING LIQUID VOLUMES IN SAID PRESSURE TRANSMITTING LEGS BETWEEN THE SEPARATE VOLUMES OF READING LIQUID, SAID PRESSURING LIQUID AND READING LIQUID BEING OF DIFFERENT SPECIFIC GRAVITIES AND NON-MISCIBLE, AND RECTIFIER RECEPTACLES BETWEEN THE SUCCESSIVE SUPPLY RECEPTACLES AND THE ATTENDED READING LEG TO ABSORB THE ACCUMULATING VOLUMES OF PRESSURING LIQUID BEFORE TRANSMITTING PRESSURES TO CAUSE MOVEMENT OF THE READING LIQUID IN THE AFFECTED READING LEG. 